Selective conversion of CO₂ to CO using earth abundant tin modified copper gas diffusion electrodes

Earth-abundant copper-tin (CuSn) electrocatalysts are potential candidates for cost-effective and sustainable production of CO from electrochemical carbon dioxide reduction (eCO₂R). However, the requirement of high-overpotential for obtaining reasonable current, low Faradaic efficiencies (FE) and low intrinsic catalytic activities require the optimisation of the CuSn nanoarchitecture for the further advancement in the field. In the current work, we have optimised Sn loading on Cu gas diffusion electrodes (GDEs) by electrochemical spontaneous precipitation. Samples with various Sn loadings were tested in a three-chamber GDE reactor to evaluate their CO₂ reduction performances. The best performance of 92% CO Faradaic efficiency at a cathodic current density of 120 mA cm⁻² was obtained from the 20 min Sn deposited Cu₂O sample operated at −1.13 V vs. RHE. The electrocatalyst had ∼13% surface coverage of Sn on Cu GDE surface, and had Sn in oxide form and copper in metallic form. The catalyst also showed stable performance and was operable for >3 h under chronoamperometric conditions. The surface of the GDE reduces from Cu₂O to Cu during eCO₂R and goes further reconstruction during the eCO₂R. This study demonstrates the potential of Cu–Sn for selective CO production at high current densities.